:root {
  --black:      #000000;
  --white:      #ffffff;
  --paper:      #f8f6f0;
  --gray-1:     #f2f0ec;
  --gray-2:     #e0ddd6;
  --gray-3:     #b0ada6;
  --gray-4:     #555555;
  --cell:       52px;
  --font-serif: Georgia, 'Times New Roman', Times, serif;
  --font-mono:  'Courier New', Courier, monospace;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
body {
  font-family: var(--font-serif);
  background-color: var(--paper);
  color: var(--black);
  line-height: 1.7;
  min-height: 100vh;
}
img, svg { display: block; max-width: 100%; }
a { color: var(--black); text-decoration: underline; }
a:hover { text-decoration: none; }
p { margin-bottom: 1rem; }
ul, ol { margin-left: 1.5rem; margin-bottom: 1rem; }
li { margin-bottom: 0.35rem; }
h1 { font-size: 2.4rem; line-height: 1.1; }
h2 { font-size: 1.75rem; line-height: 1.2; margin-bottom: 0.5rem; }
h3 { font-size: 1.3rem; line-height: 1.3; margin-bottom: 0.4rem; }
h4 { font-size: 1.05rem; margin-bottom: 0.3rem; }

.container { max-width: 1080px; margin: 0 auto; padding: 0 20px; }

.masthead {
  background: var(--white);
  border-bottom: 3px solid var(--black);
  padding: 0;
}
.masthead-date-bar {
  border-bottom: 1px solid var(--black);
  padding: 5px 20px;
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--gray-4);
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.masthead-inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 18px 20px 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.masthead-logo { text-decoration: none; display: flex; align-items: center; gap: 14px; }
.masthead-logo:hover { text-decoration: none; }
.masthead-logo img { height: 52px; width: auto; }
.masthead-titles { border-left: 2px solid var(--black); padding-left: 16px; }
.masthead-site-name {
  font-size: 2.4rem;
  font-weight: 900;
  letter-spacing: -0.03em;
  text-transform: uppercase;
  line-height: 1;
  color: var(--black);
}
.masthead-tagline {
  font-size: 0.72rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--gray-4);
  margin-top: 3px;
}
.masthead-meta {
  text-align: right;
  font-size: 0.75rem;
  color: var(--gray-4);
  line-height: 1.5;
}
.masthead-meta strong { display: block; font-size: 1.2rem; font-family: var(--font-mono); color: var(--black); }

.main-nav {
  background: var(--black);
  border-top: 1px solid var(--black);
}
.main-nav .container { display: flex; gap: 0; }
.main-nav a {
  display: inline-block;
  padding: 10px 20px;
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  font-weight: 700;
  color: var(--white);
  text-decoration: none;
  border-right: 1px solid #333;
  transition: background 0.15s;
}
.main-nav a:first-child { border-left: 1px solid #333; }
.main-nav a:hover { background: #333; }
.main-nav a.active { background: var(--white); color: var(--black); }

main { padding: 32px 0 48px; }

.game-layout {
  display: grid;
  grid-template-columns: 1fr 260px;
  gap: 28px;
  align-items: start;
}
.game-left { display: flex; flex-direction: column; align-items: center; gap: 18px; }

.game-header {
  width: 100%;
  max-width: calc(var(--cell) * 9 + 6px);
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  border-bottom: 2px solid var(--black);
  padding-bottom: 8px;
  margin-bottom: 2px;
}
.game-header h1 { font-size: 1.5rem; text-transform: uppercase; letter-spacing: 0.06em; }
.game-difficulty-label {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--gray-4);
  border: 1px solid var(--gray-3);
  padding: 2px 8px;
}

.sudoku-grid {
  display: grid;
  grid-template-columns: repeat(9, var(--cell));
  grid-template-rows:    repeat(9, var(--cell));
  border: 3px solid var(--black);
  background: var(--white);
  user-select: none;
  cursor: default;
}
.sudoku-cell {
  width:  var(--cell);
  height: var(--cell);
  border-right:  1px solid var(--gray-3);
  border-bottom: 1px solid var(--gray-3);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  background: var(--white);
  transition: background 0.08s;
  font-size: 1.45rem;
  position: relative;
}

.sudoku-cell[data-col="2"] { border-right:  3px solid var(--black); }
.sudoku-cell[data-col="5"] { border-right:  3px solid var(--black); }
.sudoku-cell[data-col="8"] { border-right:  none; }
.sudoku-cell[data-row="2"] { border-bottom: 3px solid var(--black); }
.sudoku-cell[data-row="5"] { border-bottom: 3px solid var(--black); }
.sudoku-cell[data-row="8"] { border-bottom: none; }

.sudoku-cell.given       { font-weight: 900; color: var(--black); }
.sudoku-cell.user-ok     { font-weight: 400; color: var(--gray-4); }
.sudoku-cell.user-err    { font-weight: 400; color: var(--black); text-decoration: line-through; }
.sudoku-cell.selected    { background: #c6c6c6; }
.sudoku-cell.peer        { background: var(--gray-1); }
.sudoku-cell.same-num    { background: #d4d4d4; }

.cell-notes {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows:    repeat(3, 1fr);
  width: 100%; height: 100%;
  padding: 1px;
  pointer-events: none;
}
.cell-note {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.54rem;
  font-family: var(--font-mono);
  color: var(--gray-3);
  line-height: 1;
}
.cell-note.on { color: var(--black); font-weight: bold; }

.numpad-wrap {
  width: 100%;
  max-width: calc(var(--cell) * 9 + 6px);
}
.numpad-row {
  display: flex;
  gap: 6px;
  margin-bottom: 6px;
}
.numpad-row:last-child { margin-bottom: 0; }
.num-btn {
  flex: 1;
  aspect-ratio: 1;
  border: 2px solid var(--black);
  background: var(--white);
  font-family: var(--font-serif);
  font-size: 1.35rem;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  transition: background 0.12s, color 0.12s;
  padding: 0;
}
.num-btn:hover { background: var(--black); color: var(--white); }
.num-btn.depleted { border-color: var(--gray-2); color: var(--gray-2); pointer-events: none; }
.num-remaining {
  font-size: 0.5rem;
  font-weight: 400;
  font-family: var(--font-mono);
  color: var(--gray-3);
  line-height: 1;
  margin-top: 1px;
}
.num-btn:hover .num-remaining { color: var(--gray-2); }

.ctrl-btn {
  flex: 2;
  border: 2px solid var(--black);
  background: var(--white);
  font-family: var(--font-serif);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  cursor: pointer;
  padding: 8px;
  text-align: center;
  transition: background 0.12s, color 0.12s;
  display: flex;
  align-items: center;
  justify-content: center;
}
.ctrl-btn:hover  { background: var(--black); color: var(--white); }
.ctrl-btn.active { background: var(--black); color: var(--white); }

.controls-panel {
  border: 2px solid var(--black);
  background: var(--white);
  overflow: hidden;
}
.panel-section {
  border-bottom: 1px solid var(--gray-2);
  padding: 14px 16px;
}
.panel-section:last-child { border-bottom: none; }
.panel-label {
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--gray-4);
  margin-bottom: 10px;
  font-weight: 700;
}

.timer {
  font-family: var(--font-mono);
  font-size: 2.4rem;
  font-weight: 700;
  text-align: center;
  letter-spacing: 0.08em;
  padding: 10px 0;
  border: 1px solid var(--gray-2);
  background: var(--paper);
}

.diff-group {
  display: flex;
  border: 1px solid var(--black);
  overflow: hidden;
}
.diff-btn {
  flex: 1;
  padding: 7px 4px;
  border: none;
  border-right: 1px solid var(--black);
  background: var(--white);
  font-family: var(--font-serif);
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.12s, color 0.12s;
}
.diff-btn:last-child { border-right: none; }
.diff-btn:hover  { background: var(--gray-1); }
.diff-btn.active { background: var(--black); color: var(--white); }

.panel-btn {
  display: block;
  width: 100%;
  padding: 10px 12px;
  border: 2px solid var(--black);
  background: var(--white);
  font-family: var(--font-serif);
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  cursor: pointer;
  text-align: center;
  margin-bottom: 8px;
  transition: background 0.12s, color 0.12s;
}
.panel-btn:last-child { margin-bottom: 0; }
.panel-btn:hover    { background: var(--black); color: var(--white); }
.panel-btn.primary  { background: var(--black); color: var(--white); }
.panel-btn.primary:hover { background: var(--gray-4); }

.mistakes-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.78rem;
}
.mistake-pips { display: flex; gap: 5px; }
.pip {
  width: 12px; height: 12px;
  border: 2px solid var(--black);
  border-radius: 50%;
}
.pip.filled { background: var(--black); }

.status-msg {
  font-size: 0.72rem;
  text-align: center;
  padding: 6px;
  background: var(--paper);
  border: 1px solid var(--gray-2);
  min-height: 30px;
  color: var(--gray-4);
  font-style: italic;
}

.modal-overlay {
  position: fixed; inset: 0;
  background: rgba(0,0,0,0.72);
  display: flex; align-items: center; justify-content: center;
  z-index: 999;
  opacity: 0; visibility: hidden;
  transition: opacity 0.25s, visibility 0.25s;
}
.modal-overlay.show { opacity: 1; visibility: visible; }
.modal-box {
  background: var(--white);
  border: 3px solid var(--black);
  padding: 40px 36px;
  max-width: 400px; width: 90%;
  text-align: center;
}
.modal-box h2 {
  font-size: 2rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 6px;
}
.modal-box p { font-size: 1rem; color: var(--gray-4); margin-bottom: 24px; }
.modal-stats {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 10px;
  margin-bottom: 28px;
}
.modal-stat {
  border: 1px solid var(--black);
  padding: 12px 8px;
}
.stat-val {
  display: block;
  font-family: var(--font-mono);
  font-size: 1.6rem;
  font-weight: 900;
}
.stat-label {
  display: block;
  font-size: 0.62rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--gray-4);
  margin-top: 2px;
}

footer {
  background: var(--white);
  border-top: 3px solid var(--black);
  padding: 36px 0 24px;
  margin-top: 48px;
}
.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 32px;
  margin-bottom: 28px;
}
.footer-col h4 {
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  border-bottom: 1px solid var(--black);
  padding-bottom: 6px;
  margin-bottom: 12px;
}
.footer-col ul { list-style: none; margin-left: 0; }
.footer-col ul li { margin-bottom: 5px; }
.footer-col ul li a { font-size: 0.82rem; text-decoration: none; color: var(--gray-4); }
.footer-col ul li a:hover { color: var(--black); text-decoration: underline; }
.footer-col p { font-size: 0.82rem; color: var(--gray-4); }
.footer-bottom {
  border-top: 1px solid var(--gray-2);
  padding-top: 18px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.72rem;
  color: var(--gray-4);
}
.footer-bottom a { color: var(--gray-4); }

.page-hero {
  border-bottom: 2px solid var(--black);
  padding-bottom: 20px;
  margin-bottom: 32px;
}
.page-hero h1 { margin-bottom: 6px; }
.page-hero .meta {
  font-size: 0.78rem;
  color: var(--gray-4);
  font-style: italic;
}
.legal-body h2 {
  font-size: 1.25rem;
  margin-top: 32px;
  margin-bottom: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--gray-2);
}
.legal-body h3 { font-size: 1.05rem; margin-top: 20px; margin-bottom: 6px; }
.legal-body p { font-size: 0.94rem; }
.legal-body ul, .legal-body ol { font-size: 0.94rem; }
.callout {
  border: 2px solid var(--black);
  padding: 16px 20px;
  margin: 20px 0;
  background: var(--gray-1);
}
.callout p { margin-bottom: 0; font-weight: 700; }
.two-col-legal {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 40px;
  align-items: start;
}

.about-intro {
  display: grid;
  grid-template-columns: 1fr 260px;
  gap: 40px;
  margin-bottom: 40px;
  align-items: start;
}
.how-to-play { border: 2px solid var(--black); padding: 24px; }
.how-to-play h2 { border-bottom: 1px solid var(--black); padding-bottom: 10px; margin-bottom: 18px; }
.rules-grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 18px;
  margin: 28px 0;
}
.rule-card {
  border: 1px solid var(--black);
  padding: 16px;
}
.rule-card h3 { font-size: 1rem; margin-bottom: 6px; border-bottom: 1px solid var(--gray-2); padding-bottom: 5px; }
.rule-card p  { font-size: 0.85rem; margin-bottom: 0; }
.rule-num {
  font-size: 2.5rem;
  font-weight: 900;
  font-family: var(--font-mono);
  color: var(--gray-2);
  float: right;
  line-height: 1;
}

.contact-layout {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 40px;
  align-items: start;
}
.contact-form { max-width: 100%; }
.form-group { margin-bottom: 20px; }
.form-group label {
  display: block;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-weight: 700;
  margin-bottom: 6px;
}
.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  padding: 10px 12px;
  border: 2px solid var(--black);
  background: var(--white);
  font-family: var(--font-serif);
  font-size: 0.95rem;
  color: var(--black);
  outline: none;
  transition: background 0.1s;
}
.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus { background: var(--gray-1); }
.form-group textarea { resize: vertical; min-height: 130px; }
.form-submit {
  padding: 12px 32px;
  border: 2px solid var(--black);
  background: var(--black);
  color: var(--white);
  font-family: var(--font-serif);
  font-size: 0.88rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  cursor: pointer;
  transition: background 0.12s;
}
.form-submit:hover { background: var(--gray-4); }
.contact-info { border: 2px solid var(--black); }
.contact-info-item {
  padding: 16px;
  border-bottom: 1px solid var(--gray-2);
}
.contact-info-item:last-child { border-bottom: none; }
.contact-info-item h4 { font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.15em; margin-bottom: 4px; }
.contact-info-item p  { font-size: 0.88rem; margin-bottom: 0; color: var(--gray-4); }

.rule { border: none; border-top: 1px solid var(--gray-2); margin: 28px 0; }
.rule-thick { border: none; border-top: 2px solid var(--black); margin: 28px 0; }

.breadcrumb {
  font-size: 0.75rem;
  margin-bottom: 22px;
  color: var(--gray-4);
}
.breadcrumb a { color: var(--gray-4); }
.breadcrumb span { margin: 0 6px; }

@media (max-width: 900px) {
  .game-layout    { grid-template-columns: 1fr; justify-items: center; }
  .controls-panel { width: 100%; max-width: calc(var(--cell) * 9 + 6px); }
  .about-intro    { grid-template-columns: 1fr; }
  .footer-grid    { grid-template-columns: 1fr 1fr; }
  .two-col-legal  { grid-template-columns: 1fr; }
  .contact-layout { grid-template-columns: 1fr; }
  .rules-grid     { grid-template-columns: 1fr; }
}

@media (max-width: 620px) {
  :root { --cell: 38px; }
  .masthead-inner { flex-direction: column; align-items: flex-start; gap: 10px; }
  .masthead-meta  { display: none; }
  .masthead-site-name { font-size: 1.8rem; }
  .main-nav a     { padding: 9px 12px; font-size: 0.68rem; }
  .footer-grid    { grid-template-columns: 1fr; }
  .footer-bottom  { flex-direction: column; gap: 8px; text-align: center; }
  h1 { font-size: 1.7rem; }
  h2 { font-size: 1.35rem; }
}

@media (max-width: 420px) {
  :root { --cell: 34px; }
  .masthead-logo img { height: 36px; }
  .masthead-titles { border-left: none; padding-left: 0; }
  .main-nav a { padding: 8px 9px; font-size: 0.62rem; }
  .sudoku-cell { font-size: 1.1rem; }
}